Answer:
option A " Polymerace chain reaction" (PCR)
Step-by-step explanation:
polymerace chain reaction is a method in which millions to billions copies of DNA is formed by taking small about of DNA and amplify it for further studies.
It has following three steps:
1- Denaturation : in which un-winding of DNA occur by means of heat at approx 90 degree Celsius for some seconds
2- Annealing: is a step in which DNA priming occur.
3- Extension: complementary nucleotide is added.